Problem: Solve for $z$ : $-13 + z = -29$
Explanation: Add $13$ to both sides: $ \begin{eqnarray} \\ -13 + z &=& -29 \\ \\ {+13} && {+13} \end{eqnarray} $ $ \begin{eqnarray} \hphantom{-13 + z} &\hphantom{=}& \hphantom{-29} \\ z &=& -29 {+ 13} \\ \end{eqnarray} $ Simplify. $ z = -16$